New technique helps biologists save the world's threatened seagrass meadows

Sep 30, 2013
The researchers collect seagrass tissue. Credit: Kieryn Kilminster

Danish and Australian biologists have developed a technique to determine if seagrass contain sulfur. If the seagrass contains sulfur, it is an indication that the seabed is stressed and that the water environment is threatened. The technique will help biologists all over the world in their effort to save the world's seagrass meadows.

Seagrass meadows, such as eelgrass or Halophila, grow along most of the world's coasts where they provide important habitats for a wide variety of life forms. However in many places have been lost or seriously diminished and in their effort to reestablish the meadows biologists can now benefit from a new technique that reveals the health of seagrass.

"It cannot always be seen by the naked eye if a seagrass plant is thriving or not. Therefore, it is necessary to develop methods that reveal the health state of the plant and what causes the failure to thrive. Now we have such a technique", says professor Marianne Holmer from the Department of Biology at the University of Southern Denmark. For many years she has studied the ecology and biogeochemistry of seagrass in temperate and tropical ecosystems.

Seagrass meadows grow along many coasts in the world except where harsh winds, waves and currents are too turbulent for rooted plants to remain attached to the . The meadows are not only a home for a variety of small and large animals; the leaves also help to dampen the waves and the roots help to hold the sediments of the seabed. The plants also act as particle filters that keep the water clear, and they also store carbon and nutrients.

According to Marianne Holmer, biologists today have good knowledge of how light and water quality affect seagrasses, while it is more complicated to understand how sediment conditions affect seagrasses. Together with her colleague Kieryn Kilminster from the Department of Water in Western Australia, she has now developed a technique that can detect whether the sediment conditions are a problem for the seagrasses.

"We take a small piece of plant tissue from a seagrass and bring it back to the lab. Here we analyze it in a so-called mass spectrometer, and this shows us if the plant tissue contains sulfur. If we find sulfur in the , it means that the plant has absorbed sulfide from the seabed, and this means that the seabed is not a healthy environment for the seagrass", explains Marianne Holmer.

The sulfide in the seabed is formed by the so-called sulfate-reducing bacteria. They appear, when oxygen disappears from the seabed – this can happen when the seabed is fed large amounts of organic material from algal blooms or from plankton that blooms, when nutrients are released from agricultural farming. The supply of nutrients and particles can also come from cleared coastland. When vegetation is cleared from the coastland, soil and particles are freed and flow into the water. This is a problem in e.g. Australia, where cities are growing rapidly along the coasts.

"A seagrass, which has absorbed sulfide, shows reduced growth and may die-off", explains Marianne Holmer.

When seagrasses absorb nutrients, the nutrients are bound in the plant as it grows. Seagrasses have a relatively long life cycle and nutrients will be bound for a relatively long time compared to being bound in shorter lived seaweed and plankton. If seagrasses are inhibited in growth or disappear from coastlands, bays and fjords, the nutrients become available to other, more short lived plants, and this can lead to increased growth of algae and plankton.

"Many countries are working to restore the lost meadows of seagrasses, and in this work it is important to understand when and why the plants do not thrive. With our new technology, we are now better at this", says Marianne Holmer.

Explore further: Solving the seagrass crisis

More information: Development of a 'sediment-stress' functional-level indicator for the seagrass Halophila ovalis, Ecological Indicators, Volume 36, January 2014, Pages 280.

add to favorites email to friend print save as pdf

Related Stories

Solving the seagrass crisis

Sep 24, 2013

The world's seagrass meadows are in diabolical trouble – but Australian scientists say we can still save them if we act early, even as sea levels rise.

Humble plants may save the planet

Aug 16, 2013

Marine ecologists call them seagrass meadows. They once wrapped Australia's coastline providing sanctuary and food for dugongs and turtles, habitats for fish to breed and myriad other ecosystem services such ...

Nitrogen retained through loss

May 22, 2008

The nitrogen cycle plays a major role in seagrass fields. Dutch researcher Arie Vonk studied the nitrogen dynamics of seagrasses in Indonesia. He discovered that the interaction between seagrasses, animals and microorganisms ...

Seagrass on the decline

May 15, 2013

(Phys.org) —Seagrass along Moreton Bay will drastically decline as sea levels rise, a University of Queensland study has found. The study, published in international journal Global Change Biology this week, reveals that u ...

Seagrasses can store as much carbon as forests

May 22, 2012

(Phys.org) -- Seagrasses are a vital part of the solution to climate change and, per unit area, seagrass meadows can store up to twice as much carbon as the world's temperate and tropical forests.

Recommended for you

Scientists tether lionfish to Cayman reefs

8 hours ago

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

India's ancient mammals survived multiple pressures

Apr 17, 2014

Most of the mammals that lived in India 200,000 years ago still roam the subcontinent today, in spite of two ice ages, a volcanic super-eruption and the arrival of people, a study reveals.

User comments : 0

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Continents may be a key feature of Super-Earths

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...